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Subject[PATCH 1/2] ptrace_vm: ptrace for syscall emulation virtual machines
This patch adds the new PTRACE_VM_SKIPCALL and PTRACE_VM_SKIPEXIT
tags for ptrace's addr parameter.
In this way it is possible to (eventually) get rid of PTRACE_SYSEMU
PTRACE_SYSEMU_SINGLESTEP, while providing not only the same features
but a more general support for Virtual Machines.
Part#1: tracehook based architecture independent support

renzo

Signed-off-by: Renzo Davoli <renzo@cs.unibo.it>
---
diff -Naur linux-2.6.28.2/include/linux/ptrace.h linux-2.6.28.2-vm/include/linux/ptrace.h
--- linux-2.6.28.2/include/linux/ptrace.h 2009-01-25 01:42:07.000000000 +0100
+++ linux-2.6.28.2-vm/include/linux/ptrace.h 2009-02-02 14:31:42.000000000 +0100
@@ -46,6 +46,11 @@
#define PTRACE_EVENT_VFORK_DONE 5
#define PTRACE_EVENT_EXIT 6

+/* options for new PTRACE_SYSCALL syntax*/
+#define PTRACE_SYSCALL_SKIPEXIT 0x2
+#define PTRACE_SYSCALL_SKIPCALL 0x6
+#define PTRACE_SYSCALL_MASK 0x00000006
+
#include <asm/ptrace.h>

#ifdef __KERNEL__
@@ -68,6 +73,10 @@
#define PT_TRACE_VFORK_DONE 0x00000100
#define PT_TRACE_EXIT 0x00000200

+#define PT_SYSCALL_SKIPEXIT 0x60000000
+#define PT_SYSCALL_SKIPCALL 0x40000000
+#define PT_SYSCALL_MASK 0x60000000
+
#define PT_TRACE_MASK 0x000003f4

/* single stepping state bits (used on ARM and PA-RISC) */
diff -Naur linux-2.6.28.2/include/linux/tracehook.h linux-2.6.28.2-vm/include/linux/tracehook.h
--- linux-2.6.28.2/include/linux/tracehook.h 2009-01-25 01:42:07.000000000 +0100
+++ linux-2.6.28.2-vm/include/linux/tracehook.h 2009-02-02 14:45:13.000000000 +0100
@@ -112,7 +112,7 @@
struct pt_regs *regs)
{
ptrace_report_syscall(regs);
- return 0;
+ return (task_ptrace(current) & PT_SYSCALL_SKIPCALL)?1:0;
}

/**
@@ -134,7 +134,8 @@
*/
static inline void tracehook_report_syscall_exit(struct pt_regs *regs, int step)
{
- ptrace_report_syscall(regs);
+ if (!(task_ptrace(current) & PT_SYSCALL_SKIPEXIT))
+ ptrace_report_syscall(regs);
}

/**
diff -Naur linux-2.6.28.2/kernel/ptrace.c linux-2.6.28.2-vm/kernel/ptrace.c
--- linux-2.6.28.2/kernel/ptrace.c 2009-01-25 01:42:07.000000000 +0100
+++ linux-2.6.28.2-vm/kernel/ptrace.c 2009-02-02 14:31:43.000000000 +0100
@@ -367,7 +367,7 @@
#define is_sysemu_singlestep(request) 0
#endif

-static int ptrace_resume(struct task_struct *child, long request, long data)
+static int ptrace_resume(struct task_struct *child, long request, long addr, long data)
{
if (!valid_signal(data))
return -EIO;
@@ -396,6 +396,9 @@
else
user_disable_single_step(child);

+ child->ptrace &= ~PT_SYSCALL_MASK;
+ child->ptrace |= (addr & PTRACE_SYSCALL_MASK) << 28;
+
child->exit_code = data;
wake_up_process(child);

@@ -457,12 +460,12 @@
#endif
case PTRACE_SYSCALL:
case PTRACE_CONT:
- return ptrace_resume(child, request, data);
+ return ptrace_resume(child, request, addr, data);

case PTRACE_KILL:
if (child->exit_state) /* already dead */
return 0;
- return ptrace_resume(child, request, SIGKILL);
+ return ptrace_resume(child, request, addr, SIGKILL);

default:
break;

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